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The 65th anniversary of Brown v. Board of Education is on Friday, but fights over school segregation, rather than decreasing, are becoming more common. Cities like New York and San Francisco are debating how to assign students to schools in ways that foster classroom diversity, and school secession movements — in which parents seek to form their own, majority-white districts — are accelerating.

A new report from U.C.L.A. and Penn State outlines the changes in school segregation since the landmark Supreme Court ruling named after Oliver Brown, a black father who sued to enroll his daughter, Linda, in an all-white elementary school blocks from their home in Topeka, Kan.

The court’s unanimous 1954 ruling declared separate educational facilities “inherently unequal.” But the case is one of several major civil rights rulings, alongside those on voting rights and housing discrimination, that have been substantially weakened by more recent decisions.

Today, the decreasing white share of the public school population across the country may lead some to believe that schools are becoming more integrated. But the reverse is true, according to the report. The percentage of intensely segregated schools, defined as those where less than 10 percent of the student body is white, tripled between 1988 and 2016, from 6 to 18 percent.

In “a heightened period of racial conflict in our public life,” the report warns, deepening school segregation by race and class “are very high stakes trends threatening the future.”

Liberal States Suffer Some of the Most Severe Segregation

White students now account for less than half of the nation’s public school students, and Latinos are the most deeply segregated racial group in schools, according to the researchers.

While segregation was once most severe in the former states of the Confederacy, in 2016 it was in four liberal states — New York, California, Maryland and Illinois — that black children were most likely to attend intensely segregated schools. Latinos were most likely to attend intensely segregated schools in California, New York, Texas and New Jersey.

Nationwide, 42 percent of Latino students and 40 percent of black students attended schools where less than 10 percent of their peers were white in 2016. Those numbers have been rising since 1988.

Statistics like these are no surprise after decades of court rulings that released school districts from desegregation orders, and there is no consensus among education advocates about how to respond. Some are urging broad new public policy efforts to integrate schools, while others call that goal unrealistic and even a distraction from improving the schools that currently enroll large numbers of nonwhite and low-income children.

There were some bright spots, the researchers noted. In the Midwest, the share of black children attending intensely segregated schools has steadily decreased since 2001.

‘We’re Not a Black and White District Anymore.’

With a growing population of Latino and Asian schoolchildren, segregation looks a lot different today than it did in the 1950s. Some superintendents and policymakers may believe, “We’re not a black and white district anymore, so we need to move beyond desegregation,” said Erica Frankenberg, a professor of education at Penn State and an author of the report.

Instead, she added, they should ask, “What does it mean to desegregate when we have four racial groups, and some of these racial groups also have tremendous variety within them? What does that look like?”

High-poverty, racially segregated schools typically have fewer experienced teachers, advanced courses and extracurricular opportunities. A large body of research shows that nonwhite and low-income students who attend integrated schools perform better academically, and also see long-term benefits such as higher incomes and lower rates of incarceration.

White students who attend more integrated schools are not hurt academically, and may benefit from exposure to classmates who better represent the nation’s diversity. In 2016, 48 percent of public school students were white, 26 percent were Latino, 15 percent were black and 6 percent were Asian.

According to the new report, the average white student in 2016 attended a school that was 69 percent white; the average Latino student attended a school that was 55 percent Latino; the average black student attended a school that was 47 percent black; and the average Asian student attended a school that was 24 percent Asian.

Persistent Segregation in the Suburbs

Of particular concern to the researchers were the suburbs of large cities, because demographic change there has been so rapid. Between 2006 and 2016, the proportion of white public school enrollment in those suburbs fell by 10 percentage points, to 47 percent. That diversity was not reflected in schools.

The typical suburban black or Latino child attended a school in 2016 that was three-quarters nonwhite, while the typical suburban white child attended a school that was two-thirds white.

Because so few suburbs, especially outside the South, have a history of purposeful policymaking around school integration, “Doing nothing means accepting resegregation,” the report notes.

White children who lived in large cities experienced more diversity, attending schools that were, on average, 55 percent nonwhite. But even there, white parents were clustering their children in a subset of schools; over all, white students made up only 20 percent of the students in those districts.

Is Integration the Best Solution?

The authors of the report, Professor Frankenberg, Jongyeon Ee, Jennifer Ayscue and Gary Orfield, suggest several policy remedies, such as using magnet programs and busing to draw students voluntarily to schools outside their neighborhoods and districts. They urge more federal and philanthropic investment in local experiments to increase integration, and they ask schools, particularly those in formerly white-majority suburbs, to diversify their staffs and add programming meant to serve students of color.

Still, given the long history of white resistance to desegregation efforts, and the sense of exclusion some students of color feel in majority-white schools, some education advocates remain skeptical of relying too heavily on integration as a strategy for improving educational outcomes.

“There are two ways to experience school integration policy in America: On paper and in real life,” said Derrell Bradford, executive vice president of 50CAN, an organization that supports charter schools and school choice. The goal, he said, should be to “build schools that people are attracted to, regardless of who goes to them.”

He continued, “I think schools are an important place to bring us together. But they are not the only place where the work of integrating society must happen, and in many respects, schools are not equipped to deal with the history of this nation which has separated us in the first place.”

A version of this article appears in print on , on Page A12 of the New York edition with the headline: The Persistent Threat of School Segregation. Order Reprints | Today’s Paper | Subscribe